<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>deepFlatten</title>
</head>

<body>
    <div>打开浏览器控制台查看结果</div>
    <script>
        const deepFlatten = arr =>
            [].concat(...arr.map(v => (Array.isArray(v) ? deepFlatten(v) : v)));
        console.log(deepFlatten([1, [2], [[3], 4], 5]));// [1, 2, 3, 4, 5]
    </script>
</body>

</html>